THE DISAPPEARING FISH ACT

By Dr Floor Anthoni
An article for Dive Log magazine Dec-Jan 1992-93
(Response to this article is included after this
article)
www.seafriends.org.nz/enviro/habitat/nofish93.htm
-- Seafriends home page --

Dr Floor Anthoni is a veteran
diver (since 1968) who immigrated to New Zealand in 1975. Living on the
doorstep of the first marine reserve in Leigh, he has chosen to document
New Zealand underwater life on film, a lifetime task. Having logged over
1500 dives in our waters, he claims he is now 'beginning to know the place
a little'. Floor not only dives the clear waters of our east coast and
our offshore islands but also the murky depths of west coast, rivers and
estuaries. 'Those places cause the biggest surprises', he claims.This article was written
to stimulate discussion over the havoc created by the latest 'El Nino'
weather pattern.

.
'

If a hundred dollars was all you possessed, would you notice if eighty
dollars had disappeared overnight? Of course you would, but only
when you decided to count your dollars again, which might be tomorrow or
next year. So maybe you might not notice for a while. If three quarters
of the birds around us disappeared overnight, would you notice? Probably
not because most people know very little about the animals and plants around
them. Some might have noticed something strange had happened but then again,
they might not be sure about it. See, nobody is keeping a tally of the
numbers of birds considered normal in the average garden plot. We have
no 'baseline' in place and therefore we have no proof of birds disappearing
or appearing suddenly and mysteriously. Who knows, this may have been happening
regularly!

Likewise nobody has noticed that around February 1992, about 80 to 90
percent (!) of the fish life on the Poor Knights, Mokohinau, Little Barrier
and where else too, has disappeared. The Ministry of Agriculture and Fisheries
(MAF) has now reported the loss of 30 to 50% of the entire snapper population
between North Cape and East Cape. They blame the amateur fishermen and
poachers but haven't considered the possibility that El Nino might be the
culprit. [Later they blamed an error in their computer models for it]

How then, did I discover this disaster? It happened on 15 March 1992
while I was showing the Poor Knights to two friends, both good snorkeldivers.
After finding Blue Maomao Arch empty, the groupers gone, not a single cleaner
station in South Harbour and all butterfish in the shallows there gone
too, I began to be concerned. Could it be that a disaster had happened?
From that moment on I worked more systematically in my surveys, breaking
an urchin here and there to perhaps find any takers, but even that failed.
We had excellent conditions: 25 metres visibility and the water's surface
was absolutely flat without any ripples at all, all around the islands.

We went to Jan's Tunnel, Nursery Cove, Northern Arch and then we took
the boat around both islands to find any sign of the once numerous and
big pelagic schools but we found only two small blue maomao schools with
very small individuals (15 cm). After five and a half hours of intensive
snorkelling during which we repeatedly went down to 15m, which enabled
us to survey to depths of 25m, I was absolutely sure of what I had suspected:
the Poor Knights had become a very poor shadow of its former glory. About
80 to 90 percent of most fish life had disappeared.

Although lacking scientific precision, my 'eye-o-meter' established
the following: (When I say ALL, this means OVER 95% but in some cases not
a single individual could be found)

Demoiselles: ALL big ones had disappeared and most small ones. The
groups remaining were very small. Their normal hideouts in caves
and among seaweeds were empty.

Blue maomao: ALL big ones (20cm and over) had disappeared and many
small ones. ALL big schools had gone but we found two small schools of
small individuals.

Trevally: ALL big ones gone but a small school of small ones can
be found.

Koheru: ALL big ones gone but schools of very small ones of less
that 7 cm could be found.

Schooling blennies: Of the oblique swimming blennies only very few
were left, swimming in protected niches close to the rock.

Pink Maomao: About 50% less, across the board. These were
difficult to assess.

Butterfly perch: The schools of butterfly perch had been decimated
across the board.

Cleanerfish: Crimson cleaner numbers had suffered drastically
but the rarer combfish was still found.

Sandager: Sandager's wrasse adults were still around, though in
smaller numbers but nearly ALL juveniles had disappeared. With them also
a number of cleaning stations.

Other wrasses: a loss of 70% estimated. ALL juveniles gone.

Black Angelfish: About 50% disappeared, which includes ALL
the big ones. Some juveniles were found.

Butterfish: About 50% disappeared, across the board.

I was uncertain about the following species: snapper, parore, spottie,
bluefish, mado, goatfish, john dory, stingrays. But the following appeared
normal: marblefish, hiwihiwi, banded wrasse.

So, all in all an impressive obituary. Was I dreaming? Why didn't anybody
else sound the alarm? Let's make a few dives elsewhere first, I thought,
and then come back and look again. Who knows, they might have taken a walk
around the block only to return again a little later.

The Mokohinau Islands and Little Barrier fared no better, following
more or less the list above. We found ONE mature blue maomao finally, at
Simpsons Rock! The marine reserve at Leigh appeared unaffected but when
I later dived its outer regions I noticed that the big school of blue maomao
had disappeared there too and there were perhaps only 5% of the demoiselles
left.

Back to the Poor Knights, a month later (mid April). The poor picture
had not changed. Diving the deep reefs I noticed that the reef fish might
be normal there although longfinned boarfish could not be found at the
three locations I normally found them.
I started to make enquiries. I knew that it made no sense to ask novice
divers because for them the Poor Knights are still FANTASTIC. Then I discovered
that most veterans hadn't dived very much of late. Others hadn't noticed
much. From professional fishermen came suspicion about the state of our
fishery but their catches go up and down at the best of times. Now they
were laying up their longlining boats because the poor catches couldn't
pay for the diesel. The tuna fleet of Whangarei hadn't left port at all.

As I am writing this article, winter has arrived, it is mid June now.
I am now asking YOU for help in this mystery. Can you fill in some missing
pieces? Were other places affected too? When did you notice a change? Can
you quantify it?
But first some speculations and discussions. What could have caused
this enormous disaster? The cold? Lack of food? Food poisoning? Disease?
Human activity? Temperatures have been 2 to 3 degrees lower than normal
on our east coast but the lowest temperatures were recorded for winter.
Because most of the species also occur in colder waters to the south, I
think it could not have been cold alone that caused the disaster.

Could a lack of food have done it? Most of the affected species rely
either entirely or partly on planktonic food, except for the plant eaters
who have also been affected. In February the 'blue water' came in, much
later than it normally does. That blue water may have been poor in zooplankton.
But most fish can starve for three weeks before dying [and many switch
to eating plants]. It has been recorded overseas that some species of dinoflagellates
in the plankton are poisonous, causing massive deaths to fisheries elsewhere.
Such deaths occur suddenly and in this case may have been plausible. We
have had extreme plankton blooms in spring and early summer and even now
in early winter these are causing damage to the underwater world.

Could it have been a disease? From my aquariums I know that fish diseases
can spread like fire and I can remember (1983?) the massive deaths of demoiselles
at the Poor Knights. At the time this disease seemed to affect only the
demoiselles. Everywhere dead fish bodies were found. Has anybody noticed
dead fish on the bottom or in trawl nets? I exclude human activity because
the Poor Knights are a well patrolled marine reserve and located far outside
the coastal waters, which suffer from our farms' runoff.

Why do I suspect a short and sharp decline rather than a slow and prolonged
one? In January 1992 a marine scientist (Dr Howard Choat) did a survey
of the fish at the Poor Knights and his findings showed no reason for alarm.
In mid March I found the sea lettuce gardens of the black angelfish, the
ones they graze so meticulously short, had about 4 to 6 weeks of regrowth.
That and the arrival of the blue water pointed to a relatively short period
in February. But these facts are not hard enough to stand up as proof.
In the past months I also noticed how the Poor Knights apparently 'recovered'
to the eyes of a casual observer. Most divers dive the prime dive spots
such as the arches because the fish too consider these prime real estate.
These places become repopulated from the poorer real estate at their expense.
It was quite revealing to manta-board along the rock faces in between these
prime sites, to see how depleted they really were.

If a big event has really happened, then nature must show unexpected
things as a result of it. The schools of juvenile koheru are bigger and
more numerous than ever, suggesting that their predators are on permanent
holiday. The sea gooseberries, normally floating in the upper regions of
the water as limp blobs of snot with ridges of moving hairs, breaking the
sunlight into vivid rainbow colours, now revealed that they have four very
fragile wings that they can fold out like an X-wing space fighter while
four long, scintillating whips beat rhythmically inside these cupped wings
to propel them along. At their ends they trail two long fishing lines for
catching smaller plankton. I had never been able to see this because our
many plankton feeders disturb these fragile seaspace creatures and eat
their gonads out. So what we normally saw, were dying individuals. Now
they were well and alive, which suggests that indeed most plankton eaters
had disappeared.

An adage says that every black cloud has a silver lining; each setback
opens a new opportunity, even here at the Poor Knights. On 30 May I discovered
a new school of young trevally operating in the bowl between Rikoriko Cave
and Serpent Rock. They had spread out over an area of perhaps 50 square
metres and were industriously gulping water at the surface, their dark
silvery backs raised high out of the water. These were young trevally and
they didn't have the fear the old ones seem to bring with them. We could
gently park the boat in their midst and film their gulping mouths from
almost touching distance. In the water this school could be approached
without further ado, something I had never experienced before. Here I finally
found proof that fish schools have a collective memory that enables them
to pass on experiences or rather the way to respond to certain perceived
threats. Now that the older trevally had gone, the young ones had to find
out for themselves what was harmful, and I made sure I gave them no wrong
signals.

As the various fish schools rebuild themselves, which may take a decade,
we are presented with a one in a million chance to do it right this time.
Here will be true paradise if we act in the proper way. If anyone has ever
experienced what it feels like to be accepted amidst a school of trevally,
being pushed along with them, feeling the vibrations of their tail
kicks alongside, one will agree with me that this is like 'total immersion',
an unfathomable experience. And we could achieve it with demoiselles, blue
maomao and koheru as well. What is needed is immediate action and some
restraint. We need to halt all spearfishing on the Poor Knights immediately
so that the new schools of fish do not learn to fear mankind as a predator
[At the time, spearfishing was still allowed outside two very small no-take
areas]. In the coming years we need to approach these schools frequently
but with a lot of care, making sure not to give them the wrong signals.
Once their collective memory incorporates mankind as one to be trusted,
we'll have created a dive spot second to none on earth. Are you up to this
challenge?

If you have information to support or to refute my findings, please
write to me or write to this magazine. In that manner we may be able to
learn from a weather phenomenon that was unique in a lifetime.

Dear Dave,
I read Floor Anthoni's article on disappearing fish (issue 13) with
some scepticism. I don't dive at the Poor Knights enough to know whether
or not there has been a catastrophic disappearance of fish life. However,
I do dive at the Mokohinau Islands regularly, and can say that there is
no evidence of catastrophic fish mortality/disappearance there.

As part of a study on demoiselle biology, we have been diving regularly
at the Mokohinaus during January and February of each year since 1988.
We have been making numerical surveys of of demoiselle density at the Mokohinaus
(and also Great Barrier Island and Leigh) for the last three seasons. Demoiselle
density (both of fish in the water column, and nesting territorial males)
remains unchanged and high (200 fish per 30 metre transect, and greater
than two nests/m2 respectively, if anyone is interested). Similarly, Great
Barrier Island remains a site of medium density of demoiselles and Leigh
as a site of low density (if five percent of demoiselles in the marine
reserve at Leigh are all that remains, as claimed, then we should be down
to a single nest at North Reef - there are as usual 10-20. [In 2001 there
was not a single demoiselle left - JFA]
We don't make regular census of other species but the things that we
expect to find (e.g. the blue maomao school under the lighthouse at Burgess
Island - predominantly big old fish) and the interesting rarities like
yellow banded perch, knifefish and bluefish are still about. In fact a
recent trip to the Mokohinaus was made a pleasure by the high density of
pelagic planktivores (demoiselles, blue maomao and koheru) at most of the
sites we dive.

I have no idea why Dr Anthoni saw so few fish last autumn, but I do
know that fish can be cryptic, they move a lot (especially the pelagic
planktivores), and you have to take a lot of measurements over a reasonable
spread of time to get a reliable estimate of abundance. For example, we
were intrigued to find that demoiselles are not at all site loyal during
the spawning season, but can shift over periods as short as weeks. In calm
or SW weather, Flax Island Channel on Burgess Island is prime demoiselle
territory; Archway Bay round on the NW side can be a bit of a desert. A
couple of weeks of easterlies and the situation is reversed. The fish shift,
we think, either because swell movement disrupts spawning, or currents
take the zooplankton (food) somewhere else. We don't know for sure, but
we know that if we picked a standard spot and routinely counted fish there,
sometimes we'd get zilch.

On a wider level, the idea that major changes in ocean climate are causing
catastrophic changes in oceanic biota needs to be viewed with a bit of
caution. The evidence for sustained change in ocean climate is not in my
view compelling, yet the theory is becoming quite popular. Catastrophe
theories are always popular because they are dramatic, and as a result
run the risk of enjoying popular currency in excess of their worth. This
can lead to unfortunate conclusions. For example, the quantum leap from
a 25 year low in sea temperature to a 'loss of 30 to 50 percent of the
entire snapper population between North Cape and East Cape being the result
of El Niño' (Dr Anthoni's article) is a bit of a worry. Cold seasons
do result in poor snapper spawning seasons, but these will not show up
until four or five years down the track when fish enter the fished population
as adults. If the decline in the snapper population (I seem to recall that
the MAF figure was closer to 15 percent over several years) was climate
driven, then 1987 and 1988 should have been cold and miserable summers.
They weren't, and all the evidence is that 1988 in particular was a boomer
season for little snapper.

We do need to be concerned about directional changes in the abundance
of animals and plants, particularly if there is evidence that our activities
are responsible. To detect change, we need baselines and regular monitoring
(in this Dr Anthoni and I agree), but even then we might be able to catch
the peaks and troughs of natural variation and be misled. For the moment
we might be better to concentrate on the problems of red tides, rather
than red herrings.

Yours sincerely,
Dr Ned Pankhurst
Leigh Marine Laboratory.

Floor Anthoni's reply in the same edition
of Dive Log.

Dear Dave,
Dr Ned Pankhurst's research is important in that it maintains a baseline
study for the Mokohinau Islands. Far too few baseline studies are in place.
His accurate scientific method finds no significant changes in the population
whereas my own eye-o-meter produces conflicting results. Are my results
wrong, or is there something wrong with the scientific method? As a keen
observer and photographer, I have a photographic memory of the places where
I have filmed before. These films are a kind of objective measurement.
If today, I won't be able to take similar shots, then something must have
changed.

When I do a survey of an area, in one day I do half a dozen quick dives
and almost as many snorkeldives. So if fish have moved, I must pick them
up somewhere. I agree with Dr Pankhurst that demoiselles do travel around
a lot, from one side of the island to the other, in order to catch the
incoming current. But they don't seem to change their nesting sites very
much. Like the prime real estate properties of the Poor Knights - the arches
and promontories - these prime sites are nearly fully occupied, even though
the total number of fish have diminished considerably. The demoiselles'
favourite nesting sites are on sheltered barren rock with many pockets,
and these are always occupied. In January 1993 I went back to the Mokes
to follow up on my findings, and these still hold. I was unable to find
demoiselles older than about four years. The ones nesting are mainly young
ones. Like at the Poor Knights, they have increased the sizes of their
nests, normally about the size of a hand, to as big as four hands in places.
This may be nature's way to restore the balance. They are able to defend
bigger nest sites perhaps because the predating wrasses are fewer in number.
Likewise in the Leigh reserve, demoiselles can be found nesting in the
area between Goat Island and North Reef (although in smaller numbers) but
they have disappeared from less desirable spots. These are all factors
that a scientific method ignores but that can clearly be noticed by a keen
observer.

I disagree with Dr Pankhurst that the big blue maomao are still there.
Sure enough, a few can be found at some of the prime spots, but the schools
of surface-feeding mature blue maomao, previously numerous, have disappeared
completely. Not one school can be found now. The same is true for the Poor
Knights.

Are we dealing with a catastrophe? This year in December almost all
of the kelp forest deeper than 11 metres in most of the Hauraki Gulf has
disappeared (this will be a future article in DIVELOG). We have exceptional
cases of shellfish poisoning. Sponges have disappeared from vast areas
and are still dying. If this is not a catastrophe, then what is? We are
still waiting for an accurate reassessment of the snapper stock but I have
quoted figures released in the newspapers. My claim is not that snapper
have diminished through a poor spawning season but that mature snapper
have disappeared unaccountably, like other species I have mentioned.

In looking for a possible cause, we cannot go past the fact that water
temperatures have been much lower than usual (about a full two degrees),
and also for an unusually long period (nearly two years). Unusual plankton
blooms have always accompanied El Niño years and then we have always
seen unusual deaths in the sea. But this time it has been worse than ever.
Could the Mount Pinatubo eruption have contributed? I don't claim that
this weather pattern is caused by global warming or that it will be recurring,
but I do know that small climate changes elsewhere can deviate ocean currents
slightly, resulting in disproportionately larger changes at the end of
those currents. The warm East Auckland Current is a fairly narrow stream
arriving from far away and New Zealand lies at the very end of its travel.
A deviation of only 100 kilometres would bring about major changes in the
water temperature and also to our climate. We have no measurements in place
to observe the behaviour of this current.

I have been disappointed by the scientists' disinterest in the matter.
Most scientists have specialised in a very narrow area (e.g.: "I'm a limpet
man"), so there is nobody interested in the sea as a whole. The limpet
man won't see the fish dying or the kelp disappearing and doesn't care
either. And he won't stop what he is doing in order to learn from an unusual
event. Scientists also say one cannot study one-off phenomena! It appears
as if the scientist has lost the very reason for his existence: all round
curiosity. So here is a place for the keen underwater naturalist. It is
our duty to report the changes we observe in order that scientists may
take a further interest.

In science, eventually the truth wins, if only one waits long enough.
It is now 2007 and indeed the fish at the Poor Knights and in Leigh, as
elsewhere, have declined dramatically. As predicted, there has been another
mass mortality in 2001, a rather big one, which also affected Kahawai.
Since then, Kahawai and others have not recovered. The demoiselles at Goat
Island have also disappeared, but the rot went much further.

Along the whole east coast of the North Island, from the very north
to East Cape, sea urchins have disappeared to such extent that their barren
zones have been inflitrated by seaweeds of all kind. This has also been
the case at the Poor Knights. The myth of snappers-eating-urchins-who-eat-kelp
has been proved for what it is, a myth. And marine reserves have been proved
not to protect biodiversity. The evidence is now so overwhelming that it
cannot be ignored.

In the meantime, I have discovered that the most important factor in
the sea has been overlooked: the decomposing bacteria that are necessary
for recycling nutrients in the planktonic ecosystem (the plankton
balance hypothesis). I have investigated this further with a novel
method (the DDA) to measure both bacterial
activity and biomass in fresh or sea water. With this method I proved that
our ideas about how the sea works, are wrong. My discoveries also explain
how degradation works.

While writing this addendum, an extensive chapter about the Poor Knights
is nearing completion, with over 300 underwater photographs. Visit the
marine reserves section where
it will be linked, once completed.